The present invention relates to a new and improved apparatus for positioning a shroud or pouring tube at a ladle or casting vessel bottom pour discharge nozzle and withdrawing the pouring tube therefrom when exchanging a pouring tube in normal operations or to rapidly withdraw the apparatus in an emergency situation.
It is known to use tubular shaped pouring tubes as a protective shroud around the hot metal stream flowing from a ladle or casting vessel. During the continuous casting of metals, for example, protective shrouds may be used between the casting vessel and the tundish and between the tundish and the continuous casting mold. The purpose of the protective shroud is to reduce ladle stream oxidation and to control a flowing ladle stream caused by throttling of a ladle slide gate. The shroud shields the molten metal stream issuing from the ladle from oxidizing effects of the ambient atmosphere and to permit use of a protective inert atmosphere such as argon if desired.
To reduce ladle stream oxidation a shroud holder has been devised so that shrouds made of refractory material, e.g. fused silica or alumina-graphite, could be mated to the slide gate collector nozzle of casting vessels so equipped. The mechanism was designed so that the shrouds could be easily removed for ladle changes or for lancing to open a new ladle.
Equipment has been devised for moving ladle shrouds or pouring tubes, as they will be referred to hereinafter, from a storage position to a position against the bottom of a casting vessel or ladle. Bottom pour ladles are equipped with a tubular nozzle connected to the bottom of the ladle through which hot metal may flow. Flow through the nozzle may be controlled by a slide gate valve and the pouring tube is seated against the slide gate valve to provide a protective shield around the hot metal stream flowing from the ladle nozzle to a tundish or other hot metal vessel when the slide gate is open.
In a continuous casting operation hot metal is transferred from a bottom pour ladle through a nozzle at the bottom of the ladle, a slide gate valve and pouring tube into a tundish which further directs the hot metal into moulds of the continuous casting machines. The lower end of the pouring tube is submerged below the level of hot metal in the tundish. Difficulties with placing the pouring tube in a vertical position against the ladle slide gate valve with the bottom immersed in the tundish bath because of the limited distance between the bottom of the ladle and the tundish cover have been overcome by moving the vertically disposed pouring tube from a storage location to a horizontal travel position and then finally into a vertical position aligned with the ladle nozzle and the tundish opening, the lower end of the pouring tube being submerged in the hot metal of the tundish.
Problems also arise when it is occasionally necessary to rapidly withdraw the transfer car from the vicinity of the ladle and tundish. Such problems include e.g. the occasion when the slide gate fails to function; failure of the tundish stopper rods; power failure, etc. In all of these situations major damage to the apparatus is a very real possibility. Equipment available heretofore for positioning pouring tubes at ladle bottom pour slide gate valves has not included provisions for a rapid withdrawal of the pouring tubes.